Fatigue Stress Research Articles

Neuropsychiatric Manifestations of COVID-19 Disease and Post Covid Syndrome: The Role of N Acetyl-cysteine and Acetyl-L-carnitine.

COVID-19 is associated with neuropsychiatric symptoms, such as anosmia, anxiety, depression, stress-related reactions, and psychoses. The illness can cause persistent cognitive impairment and "brain fog", suggesting chronic brain involvement. Clinical entities of ongoing symptomatic COVID-19 and Post COVID Syndrome (PCS) mainly present neuropsychiatric symptoms such as dysgeusia, headache, fatigue, anxiety, depression, sleep disturbances, and post-traumatic stress disorder. The pathophysiology of COVID-19-related brain damage is unclear, but it is linked to various mechanisms such as inflammation, oxidative stress, immune dysregulation, impaired glutamate homeostasis, glial and glymphatic damage, and hippocampal degeneration. Noteworthy is that the metabotropic receptor mGluR2 was discovered as a mechanism of internalisation of SARS-CoV-2 in Central Nervous System (CNS) cells. N-acetylcysteine (NAC) and acetyl-L-carnitine (ALC) are two supplements that have already been found effective in treating psychiatric conditions. Furthermore, NAC showed evidence in relieving cognitive symptomatology in PCS, and ALC was found effective in treating depressive symptomatology of PCS. The overlapping effects on the glutamatergic system of ALC and NAC could help treat COVID-19 psychiatric symptoms and PCS, acting through different mechanisms on the xc-mGluR2 network, with potentially synergistic effects on chronic pain and neuro-astrocyte protection. This paper aims to summarise the current evidence on the potential therapeutic role of NAC and ALC, providing an overview of the underlying molecular mechanisms and pathophysiology. It proposes a pathophysiological model explaining the effectiveness of NAC and ALC in treating COVID-19-related neuropsychiatric symptoms.

Complementary Machining – Machining Strategy for Surface Modification: A Review

All fabrication techniques utilized to manufacture metallic parts modify the surface integrity of the part. Complementary machining is a relatively recent machining strategy characterized by combining metal cutting and mechanical surface treatment. Typically, it implies that after conventional machining, the cutting insert is used reversely to modify the surface by local plastic deformation. To improve product performance, mechanical surface treatment is an additional phase in the manufacturing process chain that usually results in longer production times and higher costs. As a result, a variety of hybrid techniques have been created, such as complementary machining, which has the benefit of using conventional machine tools and their associated cutting tools. The study on complementary machining is reviewed in the article. The main focus is to assess the viability of complementary machining to modify surface integrity for enhanced properties by specifically establishing its effect on tool wear, surface roughness, microhardness, fatigue, microstructure, and residual stress state.

Analyzing the Influence of Welding Process Selection on Residual Stresses in Tube-to-Tubesheet Welded Joints

Tube-to-tubesheet joints are used in the fabrication of shell and tube type heat exchangers, steam generators, boilers, condensers, and end shields of pressure tube type nuclear reactors like CANDU (Canada Deuterium Uranium) and PHWR (Pressurized Heavy Water Reactor). The weld joints connecting the tubes to the tubesheets are of prime importance as they have a direct impact on equipment safety. In the fabrication of these critical class-1 nuclear components, full penetration weld joints are used. Typically, these full penetration weld joints are created through multi-pass Tungsten Inert Gas (TIG) welding. However, more recent techniques, such as single-pass Electron Beam Welding (EBW) and Laser Beam Welding (LBW), have also been employed for this purpose. The fabrication time of these pieces of equipment containing full penetration weld joints can be drastically reduced if single-pass welding techniques are used compared to multi-pass welding techniques. However, the residual stresses developed in these joints due to the localized heat input and the substantial constraints of the tubesheet are unknown. Different welding processes, such as TIG welding, EBW, or LBW, can lead to varying levels of residual stresses in these joints, subsequently impacting their longevity. Weld residual stress plays a significant role in the initiation of failure modes of these tube-to-tubesheet welded joints, such as stress corrosion cracking, fatigue, and corrosion fatigue.This paper analyzes the residual stresses developed at the tube-to-tubesheet interface resulting from different welding techniques, such as multi-pass TIG welding and single-pass EBW/LBW. A comprehensive three-dimensional coupled thermo-mechanical finite element analysis is employed for this purpose. The findings reveal a significant difference, with single-pass EBW exhibiting up to 32% lower residual stresses compared to multi-pass TIG welding. Additionally, the Heat Affected Zone (HAZ) in EBW is approximately 50% smaller than in TIG welding, and the equivalent distortion in EBW is reduced by 90% compared to multi-pass TIG welding. In summary, this investigation concludes that single-pass EBW offers distinct advantages for tube-to-tubesheet weld joints, including reduced residual stresses, a smaller HAZ, and lower distortions.

Analysis of tooth root three-dimensional fatigue crack initiation, propagation, and fatigue life for spur gear transmission

The gears in aviation gear systems are susceptible to fatigue fracture due to high-speed, heavy-load, and load alternation operating conditions. Therefore, a numerical calculation model with multiple mesh positions loading form has been proposed in this paper to analyze the fatigue crack initiation and propagation behavior, and to estimate the fatigue life of these gears. The fatigue life of the gear is determined by separately calculating the fatigue crack initiation life and the fatigue crack propagation life. The tooth root fatigue stress and the fatigue initiation life are calculated by the multi-axial fatigue life prediction method with the Smith-Watson-Topper criterion and the critical plane method. Afterwards, the tooth root stress–strain field is calculated in Finite element (FE) software and the stress intensity factors of the crack tip are calculated in three-dimensional (3D) crack analysis software. Then, the tooth root fatigue crack propagation trajectory and the fatigue crack propagation life are obtained separately. Finally, the influence mechanism of the loading conditions, the geometry parameters of gears, and the initial crack positions on the tooth root fatigue crack initiation life, propagation life, and fatigue crack propagation trajectory are analyzed, and a tooth fatigue test bench is built for verifying the crack propagation trajectory.

Solutions to Adolescent Depression and Anxiety: A Exercise Based Perspective

As the pace of society continues to accelerate, the frequency of mental fatigue and emotional stress that people feel in their daily lives is becoming more frequent, which has caused the prevalence of depression and anxiety to rise rapidly and has now reached alarming levels. According to the World Health Organization, a staggering 13% of the global adolescent population has been diagnosed with depression and anxiety, a silent epidemic that casts a long shadow over our youth. Based on the above background, this paper first discusses the changing dynamics of the prevalence of depression and anxiety among young people and its negative effects on them. Subsequently, the therapeutic effects of exercise are analyzed in terms of accessibility, affordability, and potential as a complementary or alternative treatment. Finally, this paper gives some suggestions for better prevention of depression and anxiety.

Sustainable innovations: Mechanical and thermal stability in palm fiber-reinforced boron carbide epoxy composites

This study reports the development of a sustainable composite material by integrating boron carbide (B4C) nanoparticles into palm fruit fiber (PFF)-reinforced epoxy matrices. The mechanical and thermal properties of these composites were thoroughly assessed, yielding promising results across key performance metrics. Tensile strength increased to 41.73 MPa with 4 % B4C, while flexural strength reached 43.29 MPa at the same concentration. Impact energy also saw an improvement, peaking at 5.6 kJ/m² with 4 % B4C. Similarly, hardness values showed an upward trend, with a Shore D value of 73. Additionally, water absorption was reduced from 7.2 % to 5.3 %, indicating enhanced moisture resistance. Thermal analysis confirmed the superior thermal stability of the composite, as shown by Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG) curves, with the maximum mass loss occurring at a higher temperature for the 4 % B4C composite. Fatigue stress testing also demonstrated improved durability, with the 4 % and 5 % composites exhibiting higher fatigue resistance over multiple cycles. The findings suggest that a 4 % concentration of boron carbide achieves an optimal balance of improved mechanical strength, durability, and thermal stability, making these composites suitable for high-performance applications while promoting environmental sustainability.

Effect of Constant Cyclic Stress Coupling on the Fatigue Behavior of 304LN Stainless Steel

The stress state of the primary circuit main pipeline is very complex mixed constant stress and periodic cyclic stress during the operation of nuclear power plants, which often affects the failure behavior of the stainless steel (SS) pipe. The fatigue behavior of 304LN SS under mixed constant stress and cyclic stress was investigated, and it was found that the coupling effect of constant stress and cyclic stress has a significant collaborative acceleration on the fatigue behavior. The research results showed that the cracks in the 304LN SS did not propagate even after 78 days under both constant load conditions of 5 KN and 7.5 KN, while the crack growth rate (CGR) of the specimen increased by about an order of magnitude when coupled with a cyclic fatigue load. The fatigue life of 304LN SS was the longest under 200 °C high-temperature water, and its life was roughly the same under 250 °C and 300 °C water. In a 300 °C high-temperature water environment, the fatigue life under the coupling of constant stress and cyclic fatigue stress is significantly lower than that under symmetric cyclic stress alone. There is a synergistic acceleration effect on the fatigue life of 304LN SS when constant stress is coupled with periodic cyclic stress, which is attributed to the combined effect of a corrosion environment and mechanical factors.

Laser Treatment Effect on Fatigue Characterizations for Steel Alloy Beam Coated with Nanoparticles

Previous work investigated the effect of nano coating for steel beams on the fatigue characterization and calculated that the coating for beams leads to modifying the fatiguelife and stress. Therefore, this work modifies the fatigue characterizations for beams by using laser treatment. The main aim of this work is to modify the fatigue properties of steel materials by using a coating surface, with nanoparticle materials, in addition to the laser treatment technique, at the same time. The experimental work was divided into three parts; first, the fabricated fatigue steel samples were coated by zinc oxide (ZnO) nanoparticle; second, treatment of the fatigue sample by laser technique using (low-high) and (high–low) loading; and finally, testing the fatigue samples to calculate the fatigue life and stress, with and without laser treatment. A scanning electron microscope (SEM) was used to study the surface morphology of the samples. In addition, the numerical technique, using the finite element, was employed to evaluate the fatigue characterizations for steel samples and the results were compared. The comparison of the numerical and experimental results shows that the maximum discrepancy did not exceed about 10.86%. Finally, the treatment of nanomaterials coated steel samples shows that the fatigue characterizations were more than 35%.

Investigating the Anisotropic Mechanical Behaviour of Steel Fibre-Reinforced Aluminium-Base Composites

Base metals are often reinforced with fibres to improve their mechanical behaviour; however, it is imperative to decide the range of fibres orientation that would yield favourable strength. In this work, using sand casting method, aluminium is reinforced with galvanized steel fibres at different orientations with the aim of investigating the anisotropic mechanical behaviour of the composites. The fibre orientations considered are 0°, 30°, 60° and 90°; while the mechanical properties evaluated are impact energy, tensile, compressive and fatigue properties. Unreinforced aluminium exhibits impact energy, elongation-at-fracture, ultimate tensile strength, and maximum compressive strength of 5.15 J, 15.88%, 72.56 MN/m2, and 231.13 MN/m2, respectively. With deviation of composite fibre orientation from 0° to 30°, 60° and 90°, impact energy decreases from 8.68 to 5.56, 4.75 and 4.61 J; elongation-at-fracture decreases from 24.58 to 17.91, 12.20 and 11.87%; ultimate tensile strength decreases from 132.70 to 89.17, 63.67 and 60.34 MN/m2; and maximum compressive strength decreases from 310.66 to 251.06, 226.91 and 209.93 MN/m2. At fatigue stress amplitude of 850 MN/m2, the fatigue life of unreinforced specimen is 26 numbers of cycles-to-failure; while the deviation of composite fibre orientation from 0° to 30°, 60° and 90° yielded reduction in fatigue life from 64 to 36, 20 and 14 numbers of cycles-to-failure. Also, reduction in fatigue stress amplitude was found to increase the fatigue life of the specimens. The fatigue limit (or endurance limit) of unreinforeced specimen, and composite specimen having 0°, 30°, 60° and 90° fibre orientations are found to be 40, 70, 45, 35 and 25 MN/m2, respectively; and the corresponding fatigue life are observed to be 35480, 199518, 112195, 10021 and 5297 numbers of cycles-to-failure, respectively. The findings in this work show that specimens with 0° fibre orientation have the highest endurance of deformation before fracture, followed by specimens with 30° fibre orientation, unreinforced specimens, specimens with 60° fibre orientation and specimens with 90° fibre orientation. This could be attributed to the fact that 0° fibre orientation offers continuous reinforcement spanning the longitudinal axis of the specimens, while fibre orientation from 30° to 90° offer areas of different degrees of shear stress concentration at fibre-matrix contacts aiding fibre-matrix debonding and crack propagation. In conclusion, this work shows that orientation of steel fibre reinforcement in aluminium matrix could be varied to achieve ranges of mechanical properties and performance needed for different practical applications.

Fatigue Life Prediction for Stud Shear Connectors Based on a Machine Learning Model

The shear connector of a steel composite bridge is designed by predicting fatigue life using the fatigue strength curves (S-N curve) based on push-out test results. The fatigue strength curves of the current design codes present only a linear relationship between the stress range and fatigue life on a log scale based on push-out experiment results. However, an alternative to the current empirical formula is necessary for the fatigue design of shear connections involving many detailed variations or high strength steel materials. This study collected and reanalyzed data from push-out fatigue tests to determine the factors influencing fatigue life and propose a machine learning-based fatigue life prediction model. The proposed machine learning model demonstrated an improvement in predictive performance of approximately 2 to 8 times compared to the existing design codes when evaluated against experimental data. Feature importance analysis based on the proposed model revealed that the stress range most significantly influenced fatigue life prediction. Model validation results indicated that the proposed model provided reliable predictions with accuracy and generalization performance. Moreover, it effectively accounted for uncertainty by incorporating features previously overlooked in existing design codes. Plans for fine-tuning pretrained models were also discussed.

Numerical Simulation of Rubber Concrete Considering Fatigue Damage Accumulation of Cohesive Zone Model.

Rubber concrete (RC) has been used in fatigue-resistant components due to its durability, yet the numerical simulation of its fatigue properties remains in its early stages. This study proposes a cohesive zone model (CZM) that accounts for the accumulation of fatigue damage at the mesoscale to investigate the fatigue performance of RC. The model integrates static and fatigue damage in the CZM, effectively capturing damage caused by fatigue loading. Validation was conducted using experimental data from the existing literature. Based on this validation, four concrete beams with varying rubber replacement rates (0%, 5%, 10%, and 15%) were tested. The CZM was employed to describe the mechanical behavior of the interface transition zones (ITZs) and the mortar interior, which were simulated and analyzed under different stress levels. The results demonstrate that the model accurately simulates crack propagation paths, interface damage evolution, and the fatigue life of RC beams under fatigue loading. A functional relationship between fatigue life and stress level was established for various rubber replacement rates. This study provides a reference model for numerical simulations of RC under fatigue loading conditions and introduces new approaches for analyzing the fatigue performance of other materials.

Synchrotron X-ray radiation study of retained austenite stability and the effect on fatigue behavior of bainitic railway steels

The effect of retained austenite stability on the fatigue performance was studied in bainitic rail steel subjected to different heat treatments, including normalizing at 900 °C and normalizing at 900 °C combined with tempering at 320 °C. The normalized steel had yield strength of 851 MPa, tensile strength of 1131 MPa, uniform elongation 7.0 %, and total elongation 17.5 %. Tempering the steel at 320 °C resulted in similar strength and plasticity compared to the normalized condition. However, the fatigue performance of steel was improved significantly after tempering. The ultimate fatigue stress (endurance limit) after 1 × 107 cycles was 671 MPa, which was 38 MPa greater than the normalized steel. Microstructural analysis revealed similarities between normalized and tempered matrices at crystallographic interfaces and grain boundaries. Synchrotron X-ray radiation indicated that the initial retained austenite content was ∼15.5 % in both normalized and tempered conditions. However, at tensile stress of 800 MPa, the amount of retained austenite transformed in the normalized steel was ∼4 %, which was twice that of the tempered steel. The enhancement of retained austenite stability was an important aspect in improving the fatigue performance. The analysis of interphase spacing showed that the strain in the normalized matrix synchronized with the retained austenite, and the stress was concentrated in the retained austenite, which promoted transformation of retained austenite. The matrix of tempered steel was strained first, which prevented stress concentration in the retained austenite and rendered the retained austenite stable.

Natural Seawater Impact on Crack Propagation and Fatigue Behavior of Welded Nickel Aluminum Bronze

ABSTRACTNickel aluminum bronze (NAB) is a complex alloy used extensively in the marine environment. Fatigue strength of NAB is reduced by welding and prior seawater corrosion. This study investigated the combined effect of corrosion and plasma welding on the fatigue behavior of NAB. Natural seawater corroded samples were used in tension‐tension cyclic loading tests to observe fatigue crack initiation, propagation, and failure. Fatigue cracks initiated from corrosion pits at the weld toe. Stress corrosion and fatigue cracks propagated along the path of β′ and κIII phases. A short crack growth model (SCGM) predicted fatigue strength using experimentally obtained material properties and corrosion pit dimensions. Model predictions were used to develop S‐N curves and were within 30% of experimental results. The SCGM produced accurate and reliable fatigue life results that could be applied by industry to aid in revalidation decision making and inspection scheduling.

Fatigue mechanisms at 450°C of a highly twined (>70%) and HIP-densified IN718 superalloy additively manufactured by laser beam powder bed fusion

Fatigue resistance at elevated temperatures is crucial for certifying aerospace structures additively manufactured by the laser beam powder bed fusion (PBF-LB) method with IN718 superalloy. This study employed a multi-step, supersolvus heat treatment process with hot isostatic pressing (HIP), called RHSA, to minimize pores and brittle phases. Stress intensity factor (△K) calculations using data from X-ray computed tomography and shape factors referencing finite element analysis (FEA) studies confirmed the suppression of △K below the threshold of conventional IN718 (∼5 MPa√m), shifting fatigue behavior to grain-structure-dominated. Despite a very high twin boundary (TB) fraction (>70%), fatigue tests at 450°C and R = 0.1 demonstrated low scatter. Slip trace analysis and high-resolution electron backscatter diffraction (EBSD) revealed that TB-induced strain concentration became prominent only at high △K, causing cracking at 45⁰ to the loading direction. The randomly oriented TBs with higher angles (60⁰) compared to high-angle grain boundaries (HAGBs) (30–40⁰) likely enhanced slip resistance and provided a net strengthening effect, which can explain the lower-than-average TB% along fracture paths. These insights suggest that a high TB fraction is not detrimental if fatigue stress is not excessive, alleviating concerns about annealing twins during defect minimization in AM IN718, allowing novel processes to improve fatigue resistance in PBF-LB IN718.

Dynamic analysis of a NiTi rotary file by using finite element analysis: Effect of cross-section and pitch length.

This study assessed stress distribution, maximum stress values and fatigue life of experimentally designed NiTi rotary files with different cross-sectional geometry and pitch length using finite element analysis (FEA). Four cross-sectional shapes (Convex triangle, S-shaped, Triple helix and Concave triangle) and two pitch lengths (2 mm and 3 mm) were tested in simulated root canals with curvatures of 30°, 45° and 60°. The FEA results indicated that convex triangle and triple helix geometries exhibited lower stress values compared to the S-shaped and concave triangle designs. Increasing the canal curvature angle resulted in higher stress values, with the S-shaped instrument showing the most significant increase (up to 12%). Instruments with shorter pitch lengths showed more even stress distribution enhancing fatigue life. The maximum stress was concentrated 5-8 mm from the tip, varying across cutting edges, with S-shaped sections experiencing the lowest forces but higher stress due to lower moments of inertia.

Factors influencing job stress in pediatric nurses during the pandemic period: Focusing on fatigue, pediatric nurse-parent partnership.

The purpose of this study was to identify the factors influencing pediatric nurses'job stress, including their level of fatigue and partnerships with the parents of patients. This investigation aimed to findings of this study may lead to the development of strategies to reduce pediatric nurse's job stress. Participants were recruited from pediatric, pediatric intensive care, and neonatal intensive care units across seven general hospitals. Eligibility requiresa minimum of 6 months of experience in pediatric nursing. The sample size was determined using the G*power program, considering various variables, including age, marital status, presence of children, and work-related characteristics, leading to a final sample size of 135, adjusted for a 10% dropout rate. Data collection was conducted through self-report questionnaires, and analysis involved frequency, percentage, mean, standard deviation, t-tests, ANOVA, and stepwise multiple regression, using SPSS Statistics 27.0. This study confirmed a significant correlation between pediatric nurses'fatigue and job stress, with higher levels of fatigue associated with increased job stress. Stepwise regression analysis showed that fatigue and age were significant predictors of job stress among pediatric nurses, explaining 23% of the variance. However, detailed analysis showed that younger nurses had lower job stress scores compared to older nurses. This result suggests that more experienced nurses may experience higher job stress due to increased responsibilities and emotional burdens. This study identified the need for effective strategies to manage fatigue and reduce job stress among pediatric nurses during the COVID-19 pandemic. Younger nurses, particularly those under 25 and between 26 and 30 years old, experience lower job stress compared to older nurses. Comprehensive support systems should be developed, including workload management, emotional support, and programs to enhance partnerships between nurses and parents. These strategies can improve job satisfaction and the quality of care provided to young patients. Additionally, they ensure a more resilient and effective healthcare workforce during pandemics and similar crises.

Analysis of short-term self-healing performance of asphalt mixture under a three-point bending fatigue test

To evaluate the self-healing performance of asphalt mixture under repeated loads, indoor three-point bending fatigue tests and self-healing tests were conducted on asphalt mixture AC-13. The stress control mode was selected to test the fatigue resistance of the mixture, and the dissipated energy recovery value and visco-elastic ratio were proposed to evaluate the self-healing performance of the mixture. The experimental results show that there is a good linear relationship between fatigue life and fatigue stress, and the damage degree to the mixture is exponentially related to the load times. The numerical dispersion of flexural tensile modulus is large, which is not suitable for evaluating the self-healing performance of the mixture. As the number of loading cycles increases, the hysteresis dissipated energy of the mixture gradually decreases and tends to stabilize. After the loading interval, due to the self-healing effect, the visco-elastic performance of the asphalt material is partially restored. The initial dissipated energy before and after interval can be used as an evaluation index for self-healing behavior, and there is a good linear relationship between the initial dissipated energy and the damage degree. Due to the deformation migration of the mixture during the initial loading stage before and after interval, the visco-elastic ratio has changed, and this change becomes more pronounced with the damage degree of the mixture, indicating that the self-healing ability of the mixture has also been improved.

Assessment of the Impact of Bone Quality and Abutment Configuration on the Fatigue Performance of Dental Implant Systems Using Finite Element Analysis (FEA).

The aim of this study was to evaluate the influence of abutment angulation, types, and bone quality on fatigue performance in dental implant systems. Three-dimensional models of maxillary 3-unit fixed implant-supported prostheses were analyzed. Abutments with different angles and types were used. Healthy bone (Hb) and resorbed bone (Rb) were used. Conducted on implants, a force of 150 N was applied obliquely, directed from the palatal to the buccal aspect, at a specific angle of 30 degrees. The stress distribution and fatigue performance were then evaluated considering the types of bone used and the angles of the three different abutments. The simulation aspect of the research was carried out utilizing Abaqus 2020 software. In all models, fatigue strengths in healthy bone were higher than in resorbed bone. Maximum stress levels were seen in models with angled implants. In almost all models with resorbed bone, fatigue performances were slightly lower. Increasing the abutment angle has been shown to increase stress levels and decrease fatigue performance in the adjacent bone and along the implant-abutment interface. In general, implants applied to healthy bone were found to have a higher success rate. It has also been suggested that multiunit abutments have beneficial effects on stress distribution and fatigue performance compared to resin cemented abutments. The type or angle of abutment and the quality of the bone can lead to biomechanical changes that affect the force distribution within the bone structure surrounding the implant. Clinicians can influence the biomechanical environment of the implant site by varying the abutment angle and type to suit the condition of bone health, potentially affecting the long-term success of implant treatment.

A novel method for shape pre-optimization of fir-tree couplings in blade-disk connections

This paper presents an innovative approach to the pre-optimization of the blade-disk fir-tree coupling, with the intent of advancing the design and analysis of such connections in turbomachinery. These couplings are subjected to extreme mechanical loads, primarily from centrifugal forces during turbine operation, compounded by aerodynamic and vibrational forces. These conditions pose substantial challenges to ensuring the structural integrity and long-term reliability of the connections. Failure of the blade-disk attachment can lead to catastrophic consequences, making the optimization of these joints crucial.The proposed pre-optimization method addresses this by optimizing the distribution of material between the blade-root, disk-post, and engaging teeth, ensuring uniform load distribution across all teeth. A novel one-dimensional radial spring model is introduced, which simplifies the representation of the joint. The method achieves accurate load-sharing without requiring knowledge of the spring stiffness values, instead relying on stiffness ratios, which in turn are approximated equal to ratios between the areas of throat cross-sections. This approach effectively balances tensile stresses, contact pressures, and, proportionally, local stress peaks, all while streamlining the design process.Validation against finite element models demonstrates the model’s accuracy across different joint configurations with varying numbers of teeth. This method serves as a foundation for more detailed analysis and future optimization efforts, including those targeting specific failure mechanisms such as fretting fatigue and peak stress mitigation. Overall, this work offers a practical and efficient approach to enhancing the performance and reliability of blade-disk connections in turbomachinery.

Static and cyclic behavior of high-performance concrete reinforced with hybrid steel fibers using notched and un-notched flexural specimen

In this paper, the static and cyclic behavior of high-performance concrete reinforced with hybrid steel fibers (HPFRCs) using notched and un-notched flexural specimen were experimentally studied. The term 'hybrid steel fibers' refers to using a combination of different steel fiber s in HPFRC mortar. Three HPFRC types, produced from an identical mortar, contained a same total fiber content of 2.0 vol% but different hybrid fiber systems as follows: 0.5, 1.0, 1.5 vol% long hooked fiber blended with 1.5, 1.0, 0.5 vol% short smooth, respectively. All flexural specimens were designed with a prism-shape having dimensions of 40 × 40 × 160 mm (width × depth × full length). Two specimen types were employed: un-notched and notched specimen with its depth of 5 mm at specimen bottom. The specimens were experimented under static and cyclic loading using a three-point bending test. Despite the lower peak static load, the notched specimen produced the higher flexural strength and critical stress intensity factor, regardless of the HPFRC types. Under cyclic loading, the number of cycles of the notched specimens showed lower than that of the un-notched specimens, for all the HPFRC types at same fatigue stress ratio. Besides, the higher static flexural strength seemed to produce the lower fatigue endurance limit, based on the proposed fatigue response curves built by regression technique.